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Biomedical subjects

K Merte

Publications and source records attributed to K Merte.

At least 19 recordsLinked to original sources
PubMed2003

Comparison of different techniques of quantitative PCR for determination of Streptococcus mutans counts in saliva samples.

Saliva samples from 16 children with current caries activity were investigated for Streptococcus mutans using three different PCR techniques, and the results were compared with those of selective cultivation on mitis salivarius agar with bacitracin (MSB) (I, II: LightCycler - competitive PCR end-point analysis; III: LightCycler - kinetic real-time analysis; IV, V: block cycler - competitive PCR end-point analysis; VI: cultivation on MSB agar). In groups I, III, IV and VI the saliva samples were analyzed directly. A DNA preparation before PCR with added competitors was carried out in groups II and V to exclude the influence of PCR inhibitors. The coefficients of correlation ranged from 0.97 to 0.98 among the competitive PCR methods, 0.8 to 0.85 for competitive vs. real-time PCR and 0.5 to 0.65 for PCR vs. cultivation methods. Competitive PCR on the real-time instrument was found to be more rapid than, comparably sensitive to, but less reproducible than competitive PCR on a block cycler.

Bacteriological Techniques↗
PubMed2000

Interaction patterns between dentin and adhesive on prepared class V cavities in vitro and in vivo.

The interface between dentin and an acetone-based single-component adhesive system (Prime&Bond 2.1, DeTrey Dentsply, Germany) was morphologically investigated by scanning electron microscopy (SEM). Interaction patterns of human teeth were correlated in vivo and in vitro. The SEM examination proved that the formation of a hybrid and an adhesive layer, the peri- and intratubular adhesive penetration, as well as hiatus and nanoleakage formation were no different on vital and nonvital dentin within the limitation of the experimental arrangement of this study.

Biomechanical Phenomena↗
PubMed2000

Two-year clinical performance of two primer adhesives on class V restorations.

The prime purpose of this clinical trial was to examine the clinical quality and retention rate of resin composite in connection with two recently developed acetone-based primer adhesives in Class V lesions according to ADA Clinical Protocol Guidelines for Dentin and Enamel Adhesive Materials. All cavities were nonretentive and predominantly in dentin (mixed Class V lesions). Total bonding was not limited either by sub-base or by base materials. All the trial restorations were placed under rubber dam. Group 1 (Version 16-135-1) and group 2 (Version 17-17-1) consisted of 42 patients with 46 trials and 38 patients with 43 fillings, respectively. The mean follow-up period and the recall response at the end of the study of group 1 were 22.8 months and 92.9% and of group 2 were 22.4 months and 94.7%. The trial restorations of both groups maintained their predominantly rated USPHS-Code Alpha level within the follow-up period. The cumulative failure rate of two trials in group 1 and four in group 2 determined a failure percentage of 4.4% and 9.3%, respectively, which is within the ADA-18 month limit of <10% Charlie. The Version KL 16-135-1 came into the market as Prime & Bond(R) 2.1, and the other one turned out to be Dyract Adhesive(R) PSA, which was primarily introduced as a single-component adhesive for compomer restorative Dyract(R) (Dentsply DeTrey, Germany).

Acetone↗
PubMed2000

Comparison of profiles of key periodontal pathogens in periodontium and endodontium.

Despite the established anatomical relationship between the periodontal and pulpal tissues, bacterial migration between endodontium and periodontium is still under discussion. The objective of this study was an investigation of profiles of periodontal pathogens in pulpal and periodontal diseases affecting the same tooth by means of 16S rRNA gene directed polymerase chain reaction (PCR). 31 intact teeth with both pulp and marginal infections were investigated. The diagnosis was based on clinical and radiological examination. Samples were taken from the gingival sulcus or periodontal pocket, respectively, with sterile paper points before trepanation of the teeth. After trepanation sterile paper points and Hedstroem files were used for taking samples from the root canal. Specific PCR methods were used to detect the presence of the following pathogens: Actinobacillus actinomycetemcomitans, Bacteroides forsythus, Eikenella corrodens, Fusobacterium nucleatum, Porphyromonas gingivalis, Prevotella intermedia and Treponema denticola. In addition, quantitative competitive PCR was used to determine the total bacterial count of the samples. The investigated pathogens were proven to be present in the endondontium in all disease categories. Particularly in endodontic samples of "chronic apical periodontitis" and "chronic adult periodontitis" profiles of the periodontal pathogens were found. The results confirmed that periodontal pathogens often accompany endodontic infections and supported the idea that the periodontic-endodontic interrelationships should be considered as critical pathways which might contribute to refractory courses of endodontic or periodontal diseases.

Adult↗
PubMed1999

Quantitative determination of Streptococcus mutans by using competitive polymerase chain reaction.

Mutans streptococci are among the range of pathogens strongly related to human dental caries. The determination of total amounts of these pathogens as well as their proportion in relation to other oral bacteria is of interest for the assessment of the risk that a patient runs of developing dental caries. This paper presents a competitive polymerase chain reaction (PCR) method for the specific quantitative determination of Streptococcus mutans which uses a homologous DNA for internal standardisation. For quantification of these bacteria, calibration curves were obtained by coamplification of known amounts of S. mutans DNA in the presence of different known amounts of the competitor DNA. The same procedure was performed with known amounts of cultured S. mutans cells. In a clinical study, the reliability of the newly developed quantitative PCR method was assessed by comparing its results with those obtained in parallel with a standard chair side culture method. The described method enables a rapid and exact determination of unknown amounts of S. mutans and could provide an efficient tool for evaluating the caries risk in a patient and to monitor the efficiency of preventive and therapeutic measures.

Adult↗
PubMed1999

Quantification of bacteria in oral samples by competitive polymerase chain reaction.

Information about the total amount of bacteria in oral samples contributes to assessment of an individual's risk of contracting dental caries or developing periodontitis and the prediction of that individual's clinical course. Since existing techniques are often time-consuming and expensive, it seemed attractive to look for alternative methods for the quantification of eubacteria. With their high specificity and sensitivity, polymerase chain-reaction (PCR) techniques have the potential of supplying fast and reliable results. We developed a method of competitive PCR for the quantification of eubacteria. We designed forward and reverse PCR primers which bind to highly conserved sequences of the bacterial 16S rRNA gene. A homologous competitor was synthesized with Escherichia coli 16S rDNA as a template, with the reverse primer and a hybrid primer which binds 67 bases downstream to the forward primer and carries the forward primer sequence at its 5' end. Specificity controls with 30 different bacterial species, 5 Archaea, 3 fungi, human astrocytoma cells, and rat hepatoblastoma cells were carried out. Results were positive for all eubacteria and negative for all other cells tested. Calibration curves were obtained by co-amplification of known amounts of E. coli cells in the presence of the homologous competitor. The developed method was successfully applied to assessment of the accumulation of bacteria during an oral hygiene cessation experiment. The competitive PCR method proved to be a reliable and fast method for the quantification of bacterial DNA and cultured eubacteria, as well as of bacteria in biological samples. It may find further applications not only in periodontology and cariology but also in other fields of medical microbiology.

Archaea↗
PubMed1996

Detection of Eikenella corrodens and Actinobacillus actinomycetemcomitans by use of the polymerase chain reaction (PCR) in vitro and in subgingival plaque.

The purpose of the present investigation was to identify 2 putative periodontal pathogens: Eikenella corrodens and Actinobacillus actinomycetemcomitans by polymerase chain reaction (PCR) in vitro and in subgingival plaque. On the basis of published sequences coding for 16S rRNA two primer pairs were designed which amplify a 410 bp sequence from E. corrodens DNA and a 547 bp fragment from A. actinomycetemcomitans DNA, respectively. As few as 50 cells could be detected from pure bacterial cultures. Each of the two primer pairs was found to be specific in that it did not give any amplification product neither with cell lysates from the respective alternative bacterium nor with lysates obtained from other putative periodontal pathogens and other bacteria. The PCR method developed turned out to be a simple, rapid and reliable diagnostic tool for the detection of the target microorganisms in clinical samples.

Aggregatibacter actinomycetemcomitans↗
PubMed1990

Fluoride and mineral redeposition in outermost layers of bovine enamel during surface softening.

Mineral and fluoride concentration changes in the outermost layers of bovine enamel (depth less than 1 micron) were measured after demineralization in unbuffered hydroxyethylcellulose gels of pH = 5.4 with an intrinsic fluoride concentration of about 0.02 ppm. A combination of two nuclear analytical techniques, Rutherford backscattering spectrometry (RBS) and proton-induced gamma ray emission spectrometry (PIGE) was applied to determine the Ca/P molar ratios and F depth profiles, respectively. When compared to deeper layers, a reduced loss of mineral content is observed for the depth range of about 0-0.1 micron corresponding well with a F concentration increase from about 500 to about 5,000 ppm in the same range. These findings are interpreted as a fluoride-induced partial remineralization of the superficial surface layer during an overall demineralization process.

Animals↗
PubMed1990

[The development of initial enamel caries--a phenomenon of interfacial reactions].

The investigation deals with earliest chemical changes in outermost enamel surfaces during initial caries development. After in vitro demineralization of enamel samples in acidulated hydroxyethylcellulose solution (pH = 5.1) for periods between 1 and 288 h the Ca/P molar ratios were determined in depths of 0.04 micron using the Rutherford Backscattering spectroscopy. The measured Ca/P ratios oscillate around the initial value. This behaviour is interpreted as a combined de/remineralization process.

Calcium↗
PubMed1990

[Clinical-epidemiological characteristic of periodontal conditions].

Clinical-epidemiological screening procedures of periodontal conditions, which support on presence or absence of gingival bleeding or periodontal pockets, underestimate the severity of periodontal disease and do not reflect disease changes. The attachment level index might be a useful adjunctive tool for characterizing the pattern of severity as well as disease changes.

Adolescent↗